Process for preparing a cap or closure

ABSTRACT

A process for producing a cap or closure comprising obtaining a polypropylene composition by sequential polymerization comprising the steps: A) polymerizing in a first reactor, preferably a slurry reactor, in the presence of a Ziegler-Natta catalyst monomers comprising propylene and optionally one or more comonomers selected from ethylene and C4-C10 alpha-olefins, to obtain a first propylene polymer fraction having a comonomer content in the range of 0.0 to 1.8 wt %, and a MFR2 in the range of from 12.0 to 40.0 g/10 min, as measured according to ISO 1133 at 230° C. under a load of 2.16 kg; B) polymerizing in a second reactor, preferably a first gas-phase reactor, monomers comprising propylene and one or more comonomers selected from ethylene and C4-C10 alpha-olefins, in the presence of the first propylene polymer fraction, to obtain a second propylene polymer fraction, wherein the polypropylene composition comprising said first and second propylene polymer fractions has an MFR2 in the range of from 12.0 to 60.0 g/10 min, as measured according to ISO 1133 at 230° C. under a load of 2.16 kg, has a comonomer content in the range of from 2.2 to 5.0 wt % and wherein the ratio of the comonomer content of component A) to the comonomer content of the polypropylene composition is 0.35 or less, C) melting, extruding and moulding the polypropylene composition in the presence of at least one nucleating agent to prepare a cap or closure; and D) exposing the cap or closure obtained in step (C) to a cooling rate of 50 K/s or more.

The present invention relates to a process for producing a cap orclosure. The process first requires the preparation of a polypropylenecomposition by sequential polymerization. More specifically, theinvention first relates to a process for producing a polypropylenecomposition comprising propylene and one or more comonomers selectedfrom ethylene and C₄-C₁₀ alpha-olefins and to the conversion of theformed polypropylene composition into a cap or closure. The inventionfurther relates to caps or closures made by the process of theinvention.

BACKGROUND

Propylene homopolymers and copolymers are suitable for many applicationssuch as packaging, textile, automotive and pipe. An important area ofapplication of propylene homopolymers and copolymers is the packagingindustry, particularly in cap and closure manufacture.

In the field of caps and closures, it is of great importance to have arapid cycle time. Cycle time is the time taken to make each cap in themoulding apparatus. A short cycle time is preferred for productionefficiency and energy consumption reduction.

It has been found that by properly combining the loop and GPR fractionsin a sequential polymerisation process, one can make a composition withfaster crystallization over a wide range of cooling rates, especially athigher cooling rates (e.g. 100 K/s or above). Faster crystallization canbe used as tool to tune the solidification process during injectionmoulding process, achieving lower cycle time. Faster crystallizationallows the use of faster cooling rates and hence faster cycle times.

WO 2019/002345 and WO 2019/002346 relate to a process for producing apolypropylene composition by sequential polymerization, thepolypropylene composition having an improved combination of highflowability, high stiffness and impact, and high level of opticalproperties. The polymers described therein have the same design conceptas those of use in the present invention however there is noappreciation in these documents that the crystallisation behaviour ofthese grades is remarkable. There is no appreciation therefore that thepolymers described therein can be used with high cooling rates in capand closure manufacture.

WO2009/021686 describes a cap or closure comprising a polypropylenecomposition comprising a random propylene ethylene copolymer withdefined ethylene content in combination with certain additives.

WO2016/116606 describes a polypropylene composition with good mechanicaland optical properties, good organoleptics and low volatiles. Thecomposition is a two component composition with bimodal comonomerdistribution.

EP3006472 describes a process for the preparation of a nucleatedpolypropylene and subjecting that polypropylene to high cooling rates.Many of the polymers exemplified therein are unimodal or lack the ratioof comonomer content required in the present case.

The present invention is based on the finding that by properly combiningthe loop and GPR fractions, one can make a composition with fastercrystallization over a wide range of cooling rates, especially at highercooling rates (e.g. 100 K/s or above). A faster crystallization can beused as tool to tune the solidification process during an injectionmoulding process to thus achieve lower cycle time. The polypropylenepolymers of the invention are therefore of particular interest in themanufacture of caps and closures where a rapid cycle time is critical.

It is also required that the comonomer present is primarily present inthe GPR fraction. This increases the impact properties of the materialbut might be expected to reduce the crystallisation speed. Remarkable,we are able to operate with a large loop gas phase comonomer splitwithout reducing the crystallisation speed. The invention thereforemaximises impact and crystallisation speed.

SUMMARY OF INVENTION

Thus, viewed from one aspect the invention provides a process forproducing a cap or closure comprising obtaining a polypropylenecomposition by sequential polymerization comprising the steps:

A) polymerizing in a first reactor, preferably a slurry reactor, in thepresence of a Ziegler-Natta catalyst, monomers comprising propylene andoptionally one or more comonomers selected from ethylene and C4-C10alpha-olefins, to obtain a first propylene polymer fraction having acomonomer content in the range of 0.0 to 1.8 wt %, and a MFR2 in therange of from 12.0 to 40.0 g/10 min, as measured according to ISO 1133at 230° C. under a load of 2.16 kg;

B) polymerizing in a second reactor, preferably a first gas-phasereactor, monomers comprising propylene and one or more comonomersselected from ethylene and C4-C10 alpha-olefins, in the presence of thefirst propylene polymer fraction, to obtain a second propylene polymerfraction,

wherein the polypropylene composition comprising said first and secondpropylene polymer fractions has an MFR2 in the range of from 12.0 to60.0 g/10 min, as measured according to ISO 1133 at 230° C. under a loadof 2.16 kg, has a comonomer content in the range of from 2.2 to 5.0 wt %and wherein the wt ratio of the comonomer content of component A) to thecomonomer content of the polypropylene composition is 0.35 or less,

C) melting, extruding and moulding the polypropylene composition in thepresence of at least one nucleating agent to prepare a cap or closure;and

D) exposing the cap or closure obtained in step (C) to a cooling rate of50 K/s or more.

Viewed from another aspect the invention provides a process forproducing a cap or closure comprising obtaining a polypropylenecomposition by sequential polymerization comprising:

A) polymerizing in a first reactor, preferably a slurry reactor, in thepresence of a Ziegler-Natta catalyst, monomers comprising propylene andoptionally one or more comonomers selected from ethylene and C4-C10alpha olefins, to obtain a first propylene polymer fraction having acomonomer content in the range of 0.0 to 1.8 wt %, and a MFR2 in therange of from 12.0 to 40.0 g/10 min, as measured according to ISO 1133at 230° C. under a load of 2.16 kg;

(B) polymerizing in a second reactor, preferably a first gas-phasereactor, monomers comprising propylene and one or more comonomersselected from ethylene and optionally C4-C10 alpha olefins, in thepresence of the first propylene polymer fraction, to obtain a secondpropylene polymer fraction,

(C) polymerizing in a third reactor, preferably a second gas-phasereactor, monomers comprising propylene and one or more comonomersselected from ethylene and optionally C4-C10 alpha olefins, in thepresence of the second propylene polymer fraction to obtain a thirdpropylene polymer fraction;

wherein the polypropylene composition comprising said first, second andthird propylene polymer fractions has an MFR2 in the range of from 12.0to 60.0 g/10 min, as measured according to ISO 1133 at 230° C. under aload of 2.16 kg, has a comonomer content in the range of from 2.2 to 5.0wt % and wherein the wt ratio of the comonomer content of component A)to the comonomer content of the polypropylene composition is 0.35 orless,

D) melting, extruding and moulding the polypropylene composition in thepresence of at least one nucleating agent to prepare a cap or closure;and

E) exposing the cap or closure obtained in step (D) to a cooling rate of50 K/s or more.

Viewed from another aspect the invention provides a cap or closurecomprising polypropylene composition and at least one nucleating agentsaid polypropylene composition having a first homo or copolymerfraction, a second copolymer fraction and optionally a third copolymerfraction, said polypropylene composition having an ethylene content of2.2 to 5.0 wt % and, wherein said polypropylene composition has

a crystallisation temperature (Tc) of at least 90° C. when subjected toa cooling rate of 10 K/s.;

a crystallisation temperature (Tc) of at least 55° C. when subjected toa cooling rate of 100 K/s.; and

a crystallisation temperature (Tc) of at least 40° C. when subjected toa cooling rate of 300 K/s.

Preferably a cap or closure as defined herein has a MFR2 in the range offrom 12.0 to 60.0 g/10 min, as measured according to ISO 1133 at 230° C.under a load of 2.16 kg, and a ratio of the comonomer content of thefirst homo or copolymer fraction to the comonomer content of thepolypropylene composition is 0.35 or less. More preferably, a cap orclosure as defined herein comprises a polypropylene composition having afirst homo or copolymer fraction, a second copolymer fraction and athird copolymer fraction.

Viewed from another aspect the invention provides a process forproducing a cap or closure comprising obtaining a polypropylenecomposition comprising a nucleating agent and a polypropylenecomposition having a first homo or copolymer fraction, a secondcopolymer fraction and optionally a third copolymer fraction, saidpolypropylene composition having an ethylene content of 2.2 to 5.0 wt %and, wherein said polypropylene composition has

a crystallisation temperature (Tc) of at least 90° C. when subjected toa cooling rate of 10 K/s.;

a crystallisation temperature (Tc) of at least 55° C. when subjected toa cooling rate of 100 K/s.; and

a crystallisation temperature (Tc) of at least 40° C. when subjected toa cooling rate of 300 K/s;

melting, extruding and moulding the polypropylene composition in thepresence of the at least one nucleating agent to prepare a cap orclosure; and

exposing the cap or closure obtained to a cooling rate of 50 K/s ormore.

Viewed from another aspect the invention provides the use of apolypropylene composition and at least one nucleating agent saidpolypropylene composition having a first homo or copolymer fraction, asecond copolymer fraction and optionally a third copolymer fraction,said polypropylene composition having an ethylene content of 2.2 to 5.0wt % and, wherein said polypropylene composition has

a crystallisation temperature (Tc) of at least 90° C. when subjected toa cooling rate of 10 K/s.;

a crystallisation temperature (Tc) of at least 55° C. when subjected toa cooling rate of 100 K/s.; and

a crystallisation temperature (Tc) of at least 40° C. when subjected toa cooling rate of 300 K/s;

to reduce the cycle time in cap or closure production.

DETAILED DESCRIPTION OF THE INVENTION

This invention concerns a process for the preparation of a cap orclosure. The process requires the preparation of the requiredpolypropylene composition followed by a step of converting thecomposition into the cap or closure.

First Embodiment

In a first embodiment, the polypropylene composition used to manufacturethe caps or closures of the invention can be made in at least two mainpolymerisation stages, e.g. two steps only. In a second embodiment, thepolypropylene composition used to manufacture the caps or closures ofthe invention can be made in at least three main polymerisation stages,e.g. three steps only.

In the first embodiment, the first and second propylene polymerfractions, according to the present invention, are produced in asequential polymerization process. The term “sequential polymerizationprocess”, in the present application, indicates that the propylenepolymer fractions are produced in a process comprising at least tworeactors connected in series. In one preferred embodiment the term“sequential polymerization process” indicates, in the presentapplication, that the reaction mixture of the first reactor, i.e. thefirst propylene polymer fraction with unreacted monomers, is conveyed,preferably directly conveyed; into a second reactor where a secondpropylene polymer fraction is obtained.

Accordingly, in the process according to the invention:

-   -   i—the first propylene polymer fraction obtained in the first        reactor generally comprises a first propylene polymer which is        produced in said first reactor,    -   ii—the second propylene polymer fraction obtained in the second        reactor generally comprises a second propylene polymer which is        produced in said second reactor.

The material produced after the second reactor is the sum of(co)polymers produced in the first reactor and in the second reactor.

Accordingly, the present process comprises at least a first reactor anda second reactor. The process may comprise at least one additionalpolymerization reactor subsequent to the second reactor. In one specificembodiment the process according to the invention consists of twopolymerization reactors, i.e. a first reactor and a second reactor. Theterm “polymerization reactor” shall indicate that the mainpolymerization takes place. Thus, in case the process consists of two ormore polymerization reactors, this definition does not exclude theoption that the overall process comprises a pre-polymerization step in apre-polymerization reactor. The term “consists of” is only a closingformulation in view of the main polymerization reactors.

In case the overall process according to the invention comprises apre-polymerization reactor, the term “first propylene polymer fraction”means the sum of (co)polymer produced in the pre-polymerization reactorand the (co)polymer produced in the first reactor.

The reactors are generally selected from slurry and gas phase reactors.The first reactor is preferably a slurry reactor and can be anycontinuous or simple stirred batch tank reactor or loop reactoroperating in bulk polymerization or slurry polymerization. By “bulkpolymerization” it is meant a process where the polymerization isconducted in a liquid monomer essentially in the absence of an inertdiluent. However, it is known to a person skilled in the art, that themonomers used in commercial production are never pure but always containaliphatic hydrocarbons as impurities. For instance, the propylenemonomer may contain up to 5% of propane as an impurity. Thus, “bulkpolymerization” preferably means a polymerization in a reaction mediumthat comprises at least 60% (wt/wt) of the monomer. According to thepresent invention, the first reactor is more preferably a loop reactor.

The second reactor is preferably a gas-phase reactor. Said gas-phasereactor can be any mechanically mixed or fluidized bed reactor orsettled bed reactor. Preferably, the gas-phase reactor comprises amechanically agitated fluidized bed reactor with gas velocities of atleast 0.2 m/sec. The gas-phase reactor of a fluidized bed type reactorcan further include a mechanical agitator to facilitate the mixingwithin the fluidized bed.

The potentially subsequent polymerization reactor or reactors is/arepreferably a gas-phase reactor.

A preferred polymerization process is a “loop-gas phase”-process, suchas developed by Borealis and known as BORSTAR™ technology. Examples ofthis polymerization process are described in EP0887379, WO2004/000899,WO2004/111095 and WO99/24478.

When the overall process according to the invention comprises apre-polymerization reactor, said pre-polymerization step takes placeprior to the polymerization in the first reactor. The pre-polymerizationstep takes place in a pre-polymerization reactor whereinpre-(co)polymerization of propylene is conducted. The pre-polymerizationreactor is of smaller size compared to the first reactor, the secondreactor and the subsequent polymerization reactor or reactors, accordingto the invention, respectively. The reaction volume of thepre-polymerization reactor can be, for example, between 0.001% and 10%of the reaction volume of the first reactor, like the loop reactor. Insaid pre-polymerization reactor, the pre-(co)polymerization of propyleneis performed in bulk or slurry, producing a propylene (co)polymer.

The operating temperature in the pre-polymerization reactor is in therange of 0 to 60° C., preferably in the range of 15 to 50° C., morepreferably in the range of 18 to 35° C.

The pressure in the pre-polymerization reactor is not critical but mustbe sufficiently high to maintain the reaction mixture in liquid phase.Thus, the pressure in the pre-polymerization reactor may be in the rangeof 20 to 100 bar, preferably in the range of 30 to 70 bar.

Hydrogen can be added in the pre-polymerization reactor in order tocontrol the molecular weight, and thus the melt flow rate MFR₂ of thepropylene (co)polymer produced in the pre-polymerization reactor.

In the first reactor of the process according to the invention, amonomer feed comprised of propylene and optionally one or morecomonomers selected from ethylene and C₄-C₁₀ alpha-olefins is fed. Incase the pre-polymerization step is present in the process, thepropylene (co)polymer produced in the pre-polymerization reactor, isalso fed into the first reactor. In the first reactor, a first propylenepolymer fraction is obtained.

The first propylene polymer fraction generally has a comonomer contentselected from ethylene and C₄-C₁₀ alpha-olefins in the range of from 0.0to 1.8 wt %, preferably in the range of from 0.1 to 1.0 wt %, morepreferably in the range of from 0.1 to 8.0 wt %, especially 0.3 to 1.5wt % even 0.5 to 1.2 wt %. wt %, relative to the total amount ofmonomers present in the first propylene polymer fraction. The firstpolymer fraction is therefore preferably a copolymer, especially acopolymer with ethylene as the sole comonomer.

Generally, the first propylene polymer fraction has a melt flow rate(MFR₂) in the range of from 12 to 40 g/10 min, preferably in the rangeof from 15 to 35 g/10 min, more preferably in the range of from 15 to 30g/10 min. The MFR₂ is determined according to ISO 1133, at a temperatureof 230° C. and under a load of 2.16 kg.

The operating temperature in the first reactor is generally in the rangeof 62 to 85° C., preferably in the range of 65 to 82° C., morepreferably in the range of 67 to 80° C.

Typically the pressure in the first reactor is in the range of 20 to 80bar, preferably in the range of 30 to 70 bar, more preferably in therange of 35 to 65 bar.

Hydrogen can be added in the first reactor in order to control themolecular weight, and thus the melt flow rate MFR₂ of the firstpropylene polymer fraction obtained in said first reactor.

Generally, the hydrogen/propylene (H₂/C₃) ratio in the first reactor isin the range of 1.5 to 6.0 mol/kmol, preferably in the range of from 1.6to 5.5 mol/kmol, more preferably in the range of from 1.7 to 5.0mol/kmol.

Generally, the ratio of one or more comonomers (selected from ethyleneand C₄-C₁₀ alpha-olefins) to C₃ (process comonomer ratio) in the firstreactor is below 14.0 mol/kmol, preferably in the range of from 1.0 to12.0 mol/kmol, more preferably in the range of from 1.0 to 10.0mol/kmol.

Generally, the reaction mixture of the first reactor is conveyed,preferably directly conveyed; into the second reactor. By “directlyconveyed” is meant a process wherein the reaction mixture of the firstreactor is led directly to the next polymerization step, i.e. the secondreactor. Monomers comprising propylene and one or more comonomersselected from ethylene and C₄-C₁₀ alpha-olefins are fed into the secondreactor. In the second reactor, a second propylene polymer fraction isobtained.

The second propylene polymer fraction contains a comonomer selected fromethylene and C₄-C₁₀ alpha-olefins.

The operating temperature in the second reactor is generally in therange of 70 to 95° C., preferably in the range of 75 to 90° C., morepreferably in the range of 78 to 88° C.

Typically the pressure in the second reactor is in the range of 5 to 50bar, preferably in the range of 15 to 40 bar.

Hydrogen can be added in the second reactor in order to control themolecular weight, and thus the melt flow rate MFR₂ of the secondpropylene polymer fraction obtained in said second reactor.

Generally, the hydrogen/propylene (H₂/C₃) ratio in the second reactor isin the range of 12.0 to 70.0 mol/kmol, preferably in the range of 15.0to 60.0 mol/kmol, more preferably in the range of 16.0 to 50.0 mol/kmol.

Generally, the ratio of one or more comonomers (selected from ethyleneand C₄-C₁₀ alpha-olefins) to C₃ (process comonomer ratio) in the secondreactor is in the range of 15.0 to 85.0 mol/kmol, preferably in therange of 20.0 to 80.0 mol/kmol, more preferably in the range of 25.0 to75.0 mol/kmol.

In the process according to the invention, the propylene polymerproduced in the first reactor, i.e. the first propylene polymer, isgenerally produced in an amount in the range of from 25 to 75 wt %,preferably in an amount in the range of from 28 to 72 wt %, morepreferably in an amount in the range of from 30 to 70 wt %.

In the process according to the invention, the propylene polymerproduced in the second reactor, i.e. the second propylene polymer, isgenerally produced in an amount in the range of from 25 to 75 wt %,preferably in an amount in the range of from 28 to 72 wt %, morepreferably in an amount in the range of from 30 to 70 wt %. The amountof the first propylene polymer and the second propylene polymer isrelative to the total sum of first propylene polymer and secondpropylene polymer.

In a preferred embodiment, the one or more comonomers selected fromethylene and C₄-C₁₀ alpha-olefins are incorporated into the reactors ofthe inventive process in different amounts resulting in a polypropylenecomposition having bimodal comonomer composition with respect to thecomonomer content of each of the propylene polymers comprised in saidpolypropylene composition, i.e. first propylene polymer and secondpropylene polymer.

In the process according to the invention, the one or more comonomersare selected from ethylene and C₄-C₁₀ alpha-olefins, preferably selectedfrom ethylene and C₄-C₈ alpha-olefins, more preferably selected fromethylene and C₄-C₆ alpha-olefins, even more preferably selected from oneor more comonomers comprising ethylene, further even more preferably thecomonomer is selected from solely ethylene, through the presentinvention.

The comonomer ratio is less than 0.35, preferably less than 0.30,especially less than 0.25. The comonomer ratio is preferably at least0.1. This ratio is the ratio of comonomer content in fraction 1/finalcomonomer content. Having a higher comonomer content in the gas phasefraction (and hence the final polymer) vs the first fraction improvesimpact behaviour without damaging the crystallisation speed.

After the polymerization in the second reactor step, the materialobtained in the second reactor is recovered by conventional proceduresknow by the person skilled in the art. The recovered material accordingto the invention is generally in the form of particles.

Second Embodiment

In a second embodiment, the process of the invention employs at leastthree main reactors:

-   -   i—the first propylene polymer fraction obtained in the first        reactor generally comprises a first propylene polymer which is        produced in said first reactor,    -   ii—the second propylene polymer fraction obtained in the second        reactor generally comprises a second propylene polymer which is        produced in said second reactor,    -   iii—the third propylene polymer fraction obtained in the third        reactor generally comprises a third propylene polymer which is        produced in said third reactor.

Accordingly, the present process may also comprise at least a firstreactor, a second reactor and a third reactor. In one specificembodiment, the process according to the invention consists of threepolymerization reactors i.e. a first reactor, a second reactor and athird reactor. The term “polymerization reactor” shall indicate that themain polymerization takes place. Thus, in case the process consists ofthree or more polymerization reactors, this definition does not excludethe option that the overall process comprises for instance apre-polymerization step in a pre-polymerization reactor. The term“consists of” is only a closing formulation in view of the mainpolymerization reactors. In case the overall process according to theinvention comprises a pre-polymerization reactor, the term “firstpropylene polymer fraction” means the sum of (co)polymer produced in thepre-polymerization reactor and the (co)polymer produced in the firstreactor.

The reactors are generally selected from slurry and gas phase reactors.The first reactor is preferably a slurry reactor and can be anycontinuous or simple stirred batch tank reactor or loop reactoroperating in bulk polymerization or slurry polymerization. By “bulkpolymerization” it is meant a process where the polymerization isconducted in a liquid monomer essentially in the absence of an inertdiluent. However, it is known to a person skilled in the art, that themonomers used in commercial production are never pure but always containaliphatic hydrocarbons as impurities. For instance, the propylenemonomer may contain up to 5% of propane as an impurity. Thus, “bulkpolymerization” preferably means a polymerization in a reaction mediumthat comprises at least 60% (wt/wt) of the monomer. According to thepresent invention, the first reactor is more preferably a loop reactor.

The second reactor is preferably a first gas-phase reactor. Said firstgas-phase reactor can be any mechanically mixed or fluidized bed reactoror settled bed reactor. Preferably, the first gas-phase reactorcomprises a mechanically agitated fluidized bed reactor with gasvelocities of at least 0.2 m/sec. The first gas-phase reactor of afluidized bed type reactor can further include a mechanical agitator tofacilitate the mixing within the fluidized bed.

The third reactor is preferably a second gas-phase reactor. Said secondgas-phase reactor can be any mechanically mixed or fluidized bed reactoror settled bed reactor. Preferably the second gas-phase reactorcomprises a mechanically agitated fluidized bed reactor with gasvelocities of at least 0.2 m/sec. The second gas-phase reactor of afluidized bed type reactor can further include a mechanical agitator tofacilitate the mixing within the fluidized bed.

The potentially subsequent polymerization reactor or reactors is/arepreferably a gas-phase reactor.

A preferred polymerization process is a “loop-gas-gas-phase”-process,such as developed by Borealis and known as BORSTAR™ technology.

When the overall process according to the invention comprises apre-polymerization reactor, said pre-polymerization step takes placeprior to the polymerization in the first reactor. The pre-polymerizationstep takes place in a pre-polymerization reactor whereinpre-(co)polymerization of propylene is conducted. The pre-polymerizationreactor is of smaller size compared to the first reactor, the secondreactor, the third reactor and the subsequent polymerization reactor orreactors, according to the invention, respectively. The reaction volumeof the pre-polymerization reactor can be, for example, between 0.001%and 10% of the reaction volume of the first reactor, like the loopreactor. In said pre-polymerization reactor, the pre-(co)polymerizationof propylene is performed in bulk or slurry, producing a propylene(co)polymer.

The operating temperature in the pre-polymerization reactor is in therange of 0 to 60° C., preferably in the range of 15 to 50° C., morepreferably in the range of 18 to 35° C.

The pressure in the pre-polymerization reactor is not critical but mustbe sufficiently high to maintain the reaction mixture in liquid phase.Thus, the pressure in the pre-polymerization reactor may be in the rangeof 20 to 100 bar, preferably in the range of 30 to 70 bar.

Hydrogen can be added in the pre-polymerization reactor in order tocontrol the molecular weight, and thus the melt flow rate MFR₂ of thepropylene (co)polymer produced in the pre-polymerization reactor.

In the first reactor of the process according to the invention, amonomer feed comprised of propylene and optionally one or morecomonomers selected from ethylene and C₄-C₁₀ alpha-olefins is fed. Incase the pre-polymerization step is present in the process, thepropylene (co)polymer produced in the pre-polymerization reactor, isalso fed into the first reactor. In the first reactor, a first propylenepolymer fraction is obtained.

The first propylene polymer fraction generally has a comonomer contentselected from ethylene and C₄-C₁₀ alpha-olefins in the range of from 0.0to 1.8 wt %, preferably in the range of from 0.1 to 1.0 wt %, morepreferably in the range of from 0.1 to 8.0 wt %, especially 0.3 to 1.5wt % even 0.5 to 1.2 wt %.

Generally, the first propylene polymer fraction has a melt flow rate(MFR₂) in the range of from 12 to 40 g/10 min, preferably in the rangeof from 15 to 35 g/10 min, more preferably in the range of from 15 to 30g/10 min. The MFR₂ is determined according to ISO 1133, at a temperatureof 230° C. and under a load of 2.16 kg.

The operating temperature in the first reactor is generally in the rangeof 62 to 85° C., preferably in the range of 65 to 82° C., morepreferably in the range of 67 to 80° C.

Typically the pressure in the first reactor is in the range of 20 to 80bar, preferably in the range of 30 to 70 bar, more preferably in therange of 35 to 65 bar.

Hydrogen can be added in the first reactor in order to control themolecular weight, and thus the melt flow rate MFR₂ of the firstpropylene polymer fraction obtained in said first reactor.

Generally, the hydrogen/propylene (H₂/C₃) ratio in the first reactor isin the range of 1.5 to 6.0 mol/kmol, preferably in the range of from 1.6to 5.5 mol/kmol, more preferably in the range of from 1.7 to 5.0mol/kmol.

Generally, the ratio of one or more comonomers (selected from ethyleneand C₄-C₁₀ alpha-olefins) to C₃ in the first reactor is below 10.0mol/kmol, preferably in the range of from 0.0 to 8.0 mol/kmol, morepreferably in the range of from 0.0 to 7.5 mol/kmol.

Generally, the reaction mixture of the first reactor is conveyed,preferably directly conveyed; into the second reactor. By “directlyconveyed” is meant a process wherein the reaction mixture of the firstreactor is led directly to the next polymerization step, i.e. the secondreactor. Monomers comprising propylene and one or more comonomersselected from ethylene and C₄-C₁₀ alpha-olefins are fed into the secondreactor. In the second reactor, a second propylene polymer fraction isobtained.

The second propylene polymer fraction comprises a comonomer contentselected from ethylene and C₄-C₁₀ alpha-olefins. The material producedafter the second reactor (i.e. the sum of the first and second polymerfractions) may have a comonomer content in the range of from 0.3 to 2.0wt %, preferably in the range of from 0.5 to 1.7 wt %, more preferablyin the range of from 0.6 to 1.5 wt %.

Generally, the material produced after the second reactor (i.e. the sumof the first and second polymer fractions) may have a melt flow rate(MFR₂) in the range of from 11 to 60 g/10 min, preferably in the rangeof from 15 to 40 g/10 min, more preferably in the range of from 17 to 35g/10 min. The MFR₂ is determined according to ISO 1133, at a temperatureof 230° C. and under a load of 2.16 kg.

The operating temperature in the second reactor is generally in therange of 70 to 95° C., preferably in the range of 75 to 90° C., morepreferably in the range of 78 to 88° C.

Typically the pressure in the second reactor is in the range of 5 to 50bar, preferably in the range of 15 to 40 bar.

Hydrogen can be added in the second reactor in order to control themolecular weight, and thus the melt flow rate MFR₂ of the secondpropylene polymer fraction obtained in said second reactor.

Generally, the hydrogen/propylene (H₂/C₃) ratio in the second reactor isin the range of 12.0 to 70.0 mol/kmol, preferably in the range of 15.0to 60.0 mol/kmol, more preferably in the range of 16.0 to 50.0 mol/kmol.

Generally, the ratio of one or more comonomers (selected from ethyleneand C₄-C₁₀ alpha-olefins) to C₃ in the second reactor is in the range of4.5 to 20.0 mol/kmol, preferably in the range of 5.0 to 18.0 mol/kmol,more preferably in the range of 5.5 to 17.0 mol/kmol.

Generally, the reaction mixture of the second reactor is conveyed,preferably directly conveyed; into the third reactor. By “directlyconveyed” is meant a process wherein the reaction mixture of the secondreactor is led directly to the next polymerization step, i.e. the thirdreactor. Monomers comprising propylene and one or more comonomersselected from ethylene and C₄-C₁₀ alpha-olefins are fed into the thirdreactor. In the third reactor, a third propylene polymer fraction isobtained.

The third propylene copolymer fraction generally comprises a comonomerselected from ethylene and C₄-C₁₀ alpha-olefins.

The operating temperature in the third reactor is generally in the rangeof 70 to 95° C., preferably in the range of 75 to 90° C., morepreferably in the range of 78 to 88° C.

Typically, the pressure in the third reactor is in the range of 5 to 50bar, preferably in the range of 15 to 40 bar.

Hydrogen can be added in the third reactor in order to control themolecular weight, and thus the melt flow rate MFR₂ of the thirdpropylene polymer fraction obtained in said third reactor.

Generally the hydrogen/propylene (H₂/C₃) ratio in the third reactor isin the range of 15.0 to 80.0 mol/kmol, preferably in the range of 17.0to 70.0 mol/kmol, more preferably in the range of 19.0 to 60.0 mol/kmol.

Generally the ratio of one or more comonomers (selected from ethyleneand C₄-C₁₀ alpha-olefins) to C₃ in the third reactor is in the range of45.0 to 200.0 mol/kmol, preferably in the range of 50.0 to 180.0mol/kmol, more preferably in the range of 55.0 to 170.0 mol/kmol.

In the process according to the invention, the propylene polymerproduced in the first reactor i.e. the first propylene polymer isgenerally produced in an amount in the range of from 20 to 55 wt %,preferably in an amount in the range of from 25 to 55 wt %, morepreferably in an amount in the range of from 30 to 50 wt %.

In the process according to the invention, the propylene polymerproduced in the second reactor i.e. the second propylene polymer isgenerally produced in an amount in the range of from 30 to 70 wt %,preferably in an amount in the range of from 35 to 70 wt %, morepreferably in an amount in the range of from 35 to 55 wt %.

In the process according to the invention, the propylene polymerproduced in the third reactor i.e. the third propylene polymer isgenerally produced in an amount in the range of from 6 to 20 wt %,preferably in an amount in the range of from 7 to 15 wt %, morepreferably in an amount in the range of from 8 to 15 wt %. The amount ofthe first propylene polymer, the second propylene polymer and the thirdpropylene polymer is relative to the total sum of first propylenepolymer, second propylene polymer and third propylene polymer comprisedin the material.

In a preferred embodiment, the one or more comonomers selected fromethylene and C₄-C₁₀ alpha-olefins are incorporated into the reactors ofthe inventive process in different amounts resulting in a polypropylenecomposition having trimodal comonomer distribution with respect to thecomonomer content of each of the propylene polymers comprised in saidcomposition, i.e. first propylene polymer, second propylene polymer andthird propylene polymer.

In the process according to the invention, the one or more comonomersare selected from ethylene and C₄-C₁₀ alpha-olefins, preferably selectedfrom ethylene and C₄-C8 alpha-olefins, more preferably selected fromethylene and C₄-C₆ alpha-olefins, even more preferably selected from oneor more comonomers comprising ethylene, further even more preferably thecomonomer is selected from solely ethylene, through the presentinvention.

The comonomer ratio is less than 0.35, preferably less than 0.3,especially less than 0.25. The comonomer ratio is preferably at least0.1. This ratio is the comonomer content in fraction 1/final comonomercontent. Having a higher comonomer content in the gas phase fraction vsthe first fraction improves impact behaviour without damaging thecrystallisation speed.

After the polymerization in the third reactor step, the polymer obtainedin the third reactor is recovered by conventional procedures know by theperson skilled in the art. The recovered polymer according to theinvention is generally in the form of particles.

Catalyst

Generally, a polymerization catalyst is present in the process accordingto the invention. The polymerization catalyst is preferably aZiegler-Natta catalyst. Generally, the polymerization Ziegler-Nattacatalyst comprises one or more compounds of a transition metal (TM) ofGroup 4 to 6 as defined in IUPAC version 2013, like titanium, further aGroup 2 metal compound, like a magnesium compound and an internal donor(ID).

The components of the catalyst may be supported on a particulatesupport, such as for example an inorganic oxide, like for example silicaor alumina. Alternatively, a magnesium halide may form the solidsupport. It is also possible that the catalyst components are notsupported on an external support, but the catalyst is prepared by anemulsion-solidification method or by a precipitation method, as iswell-known by the man skilled in the art of catalyst preparation.

Preferably, a specific type of Ziegler-Natta catalyst is present in theprocess according to the invention. In this specific type ofZiegler-Natta catalyst, it is essential that the internal donor is anon-phthalic compound. Preferably, through the whole specific type ofZiegler-Natta catalyst preparation no phthalate compound is used, thusthe final specific type of Ziegler-Natta catalyst does not contain anyphthalic compound. Thus, the specific type of Ziegler-Natta catalyst isfree of phthalic compound. Therefore, the polymer obtained in the secondreactor of the process according to the invention is free of phthaliccompound.

Generally, the specific type of Ziegler-Natta catalyst comprises aninternal donor (ID) which is chosen to be a non-phthalic compound, inthis way the specific type of Ziegler-Natta catalyst is completely freeof phthalic compound. Further, the specific type of Ziegler-Nattacatalyst can be a solid catalyst preferably being free of any externalsupport material, like silica or MgCl₂, and thus the solid catalyst isself-supported.

The solid catalyst is obtainable by the following general procedure:

a) providing a solution of

-   -   a₁) at least a Group 2 metal alkoxy compound (Ax) being the        reaction product of a Group 2 metal compound and an alcohol (A)        comprising in addition to the hydroxyl moiety at least one ether        moiety, optionally in an organic liquid reaction medium; or    -   a₂) at least a Group 2 metal alkoxy compound (Ax') being the        reaction product of a Group 2 metal compound and an alcohol        mixture of the alcohol (A) and a monohydric alcohol (B) of        formula ROH, optionally in an organic liquid reaction medium; or    -   a₃) a mixture of the Group 2 metal alkoxy compound (Ax) and a        Group 2 metal alkoxy compound (Bx) being the reaction product of        a Group 2 metal compound and the monohydric alcohol (B),        optionally in an organic liquid reaction medium; or    -   a₄) Group 2 metal alkoxy compound of formula        M(OR₁)_(n)(OR₂)_(m)X_(2−n−m) or mixture of Group 2 alkoxides        M(OR₁)_(n′)X_(2−n′) and M(OR₂)_(m′)X_(2−m′), where M is a Group        2 metal, X is halogen, R₁ and R₂ are different alkyl groups of 2        to 16 carbon atoms, and 0≤n<2, 0≤m<2 and n+m+(2−n−m)=2, provided        that n and m are not 0 simultaneously, 0<n′<2 and 0<m′≤2; and

b) adding said solution from step a) to at least one compound of atransition metal of Group 4 to 6 and

c) obtaining the solid catalyst component particles, and adding anon-phthalic internal electron donor (ID) at least in one step prior tostep c).

The internal donor (ID) or precursor thereof is preferably added to thesolution of step a) or to the transition metal compound before addingthe solution of step a).

According to the procedure above, the solid catalyst can be obtained viaa precipitation method or via an emulsion—solidification methoddepending on the physical conditions, especially the temperature used insteps b) and c). An emulsion is also called liquid-liquid two-phasesystem. In both methods (precipitation or emulsion-solidification) thecatalyst chemistry is the same.

In the precipitation method, combination of the solution of step a) withat least one transition metal compound in step b) is carried out and thewhole reaction mixture is kept at least at 50° C., more preferably in atemperature range of 55 to 110° C., more preferably in a range of 70 to100° C., to secure full precipitation of the catalyst component in theform of solid catalyst component particles (step c).

In the emulsion-solidification method, in step b) the solution of stepa) is typically added to the at least one transition metal compound at alower temperature, such as from −10 to below 50° C., preferably from −5to 30° C. During agitation of the emulsion the temperature is typicallykept at −10 to below 40° C., preferably from −5 to 30° C. Droplets ofthe dispersed phase of the emulsion form the active catalystcomposition. Solidification (step c) of the droplets is suitably carriedout by heating the emulsion to a temperature of 70 to 150° C.,preferably to 80 to 110° C. The catalyst prepared by theemulsion-solidification method is preferably used in the presentinvention.

In step a) preferably the solution of a₂) or a₃) is used, i.e. asolution of (Ax′) or a solution of a mixture of (Ax) and (Bx).

Preferably, the Group 2 metal is magnesium. The magnesium alkoxycompounds (Ax), (Ax′), (Bx) can be prepared in situ in the first step ofthe catalyst preparation process, step a), by reacting the magnesiumcompound with the alcohol(s) as described above. Another option is toprepare said magnesium alkoxy compounds separately or they can be evencommercially available as already prepared magnesium alkoxy compoundsand used as such in the catalyst preparation process of the invention.

Illustrative examples of alcohols (A) are glycol monoethers. Preferredalcohols (A) are C₂ to C₄ glycol monoethers, wherein the ether moietiescomprise from 2 to 18 carbon atoms, preferably from 4 to 12 carbonatoms. Preferred examples are 2-(2-ethylhexyloxy) ethanol, 2-butyloxyethanol, 2-hexyloxy ethanol and 1,3-propylene-glycol-monobutyl ether,3-butoxy-2-propanol, with 2-(2-ethylhexyloxy) ethanol and1,3-propylene-glycol-monobutyl ether, 3-butoxy-2-propanol beingparticularly preferred.

The illustrative monohydric alcohol (B) is represented by the structuralformula ROH with R being a straight-chain or branched C₂-C₁₆ alkylresidue, preferably a Cato Cio alkyl residue, more preferably a C₆ to C₈alkyl residue. The most preferred monohydric alcohol is2-ethyl-1-hexanol or octanol.

Preferably, a mixture of Mg alkoxy compounds (Ax) and (Bx) or a mixtureof alcohols (A) and (B), respectively, are used and employed in a moleratio of Bx:Ax or B:A from 10:1 to 1:10, more preferably 6:1 to 1:6,still more preferably 5:1 to 1:3, most preferably 5:1 to 3:1.

The magnesium alkoxy compound may be a reaction product of alcohol(s),as defined above and a magnesium compound selected from dialkylmagnesium, alkyl magnesium alkoxide, magnesium dialkoxide, alkoxymagnesium halide and alkyl magnesium halide. Further, magnesiumdialkoxide, magnesium diaryloxide, magnesium aryloxyhalide, magnesiumaryloxide and magnesium alkyl aryloxide can be used. Alkyl groups in themagnesium compound can be similar or different C₁-C₂₀ alkyl groups,preferably C₂-C₁₀ alkyl groups. Typical alkyl-alkoxy magnesiumcompounds, when used, are ethyl magnesium butoxide, butyl magnesiumpentoxide, octyl magnesium butoxide and octyl magnesium octoxide.Preferably the dialkyl magnesiums are used. Most preferred, dialkylmagnesiums are butyl octyl magnesium or butyl ethyl magnesium.

It is also possible that the magnesium compound reacts in addition tothe alcohol (A) and alcohol (B) with a polyhydric alcohol (C) of formulaR″(OH)_(m) to obtain said magnesium alkoxide compound. Preferredpolyhydric alcohols, if used, are alcohols, wherein R″ is astraight-chain, cyclic or branched C₂ to C₁₀ hydrocarbon residue and mis an integer of 2 to 6.

The magnesium alkoxy compounds of step a) are thus selected from thegroup consisting of magnesium dialkoxides, diaryloxy magnesiums,alkyloxy magnesium halides, aryloxy magnesium halides, alkyl magnesiumalkoxides, aryl magnesium alkoxides and alkyl magnesium aryloxides or amixture of magnesium dihalide and a magnesium dialkoxide.

The solvent to be employed for the preparation of the present catalystmay be selected from among aromatic and aliphatic straight-chain,branched and cyclic hydrocarbons with 5 to 20 carbon atoms, morepreferably 5 to 12 carbon atoms, or mixtures thereof. Suitable solventsinclude benzene, toluene, cumene, xylol, pentane, hexane, heptane,octane and nonane. Hexanes and pentanes are particularly preferred.

The reaction for the preparation of the magnesium alkoxy compound may becarried out at a temperature of 40 to 70° C. The man skilled in the artknows how to select the most suitable temperature depending on the Mgcompound and alcohol(s) used.

The transition metal (TM) compound of Group 4 to 6 as defined in IUPACversion 2013 is preferably a titanium compound, most preferably atitanium halide, like TiCl₄.

The non-phthalic internal donor (ID) used in the preparation of thespecific type of Ziegler-Natta catalyst used in the present invention ispreferably selected from (di)esters of non-phthalic carboxylic(di)acids, 1,3-diethers, derivatives and mixtures thereof. An especiallypreferred donor is a diester of mono-unsaturated non-phthalicdicarboxylic acids, in particular an ester belonging to a groupcomprising malonates, maleates, succinates, citraconates, glutarates,cyclohexene-1,2-dicarboxylates and benzoates and derivatives thereofand/or mixtures thereof. Preferred examples are e.g. substitutedmaleates and citraconates, most preferably citraconates.

Here and hereinafter the term derivative includes substituted compounds.

In the emulsion-solidification method, the two phase liquid-liquidsystem may be formed by simple stirring and optionally adding (further)solvent(s) and/or additives, such as a turbulence minimizing agent (TMA)and/or an emulsifying agent and/or an emulsion stabilizer, like asurfactant, which are used in a manner known in the art. These solventsand/or additives are used to facilitate the formation of the emulsionand/or stabilize it. Preferably, surfactants are acrylic or methacrylicpolymers. Particularly preferred are unbranched C₁₂ to C₂₀(meth)acrylates such as for example poly(hexadecyl)-methacrylate andpoly(octadecyl)-methacrylate and mixtures thereof. The turbulenceminimizing agent (TMA), if used, is preferably selected from polymers ofα-olefin monomers with 6 to 20 carbon atoms, like polyoctene,polynonene, polydecene, polyundecene or polydodecene or mixturesthereof. Most preferable it is polydecene.

The solid particulate product obtained by the precipitation oremulsion—solidification method may be washed at least once, preferablyat least twice, most preferably at least three times. The washing cantake place with an aromatic and/or aliphatic hydrocarbon, preferablywith toluene, heptane or pentane. Washing is also possible with TiCl₄optionally combined with the aromatic and/or aliphatic hydrocarbon.Washing liquids can also contain donors and/or compounds of Group 13,like trialkyl aluminium, halogenated alky aluminium compounds or alkoxyaluminium compounds. Aluminium compounds can also be added during thecatalyst synthesis. The catalyst can further be dried, for example byevaporation or flushing with nitrogen or it can be slurried to an oilyliquid without any drying step.

The finally obtained specific type of Ziegler-Natta catalyst isdesirably obtained in the form of particles having generally an averageparticle size range of 5 to 200 μm, preferably 10 to 100 μm. Theparticles are generally compact with low porosity and have generally asurface area below 20 g/m², more preferably below 10 g/m². Typically,the amount of Ti present in the catalyst is in the range of 1 to 6 wt %,the amount of Mg is in the range of 10 to 20 wt % and the amount ofinternal donor present in the catalyst is in the range of 10 to 40 wt %of the catalyst composition. A detailed description of the preparationof the catalysts used in the present invention is disclosed inWO2012/007430, EP2610271 and EP2610272 which are incorporated here byreference.

An external donor (ED) is preferably present as a further component inthe polymerization process according to the invention. Suitable externaldonors (ED) include certain silanes, ethers, esters, amines, ketones,heterocyclic compounds and blends of these. It is especially preferredto use a silane. It is most preferred to use silanes of the generalformula (I)

R^(a) _(p)R^(b) _(q)Si(OR^(c))_((4−p−c))  (I)

wherein R^(a), R^(b) and R^(c) denote a hydrocarbon radical, inparticular an alkyl or cycloalkyl group, and wherein p and q are numbersranging from 0 to 3 with their sum (p+q) being equal to or less than 3.R^(a), R^(b) and R^(c) can be chosen independently from one another andcan be the same or different. Specific examples of silanes according toformula (I) are (tert-butyl)₂Si(OCH₃)₂, (cyclohexyl)(methyl)Si(OCH₃)₂,(phenyl)₂Si(OCH₃)₂ and (cyclopentyl)₂Si(OCH₃)₂. Another most preferredsilane is according to the general formula (II)

Si(OCH₂CH₃)₃(NR³R⁴)  (II)

wherein R³ and R⁴ can be the same or different and represent a linear,branched or cyclic hydrocarbon group having 1 to 12 carbon atoms. It isin particular preferred that R³ and R⁴ are independently selected fromthe group consisting of methyl, ethyl, n-propyl, n-butyl, octyl,decanyl, iso-propyl, iso-butyl, iso-pentyl, tert.-butyl, tert.-amyl,neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl.Most preferably ethyl is used.

Generally, in addition to the Ziegler-Natta catalyst or the specifictype of Ziegler-Natta catalyst and the optional external donor (ED) aco-catalyst (Co) can be present in the polymerization process accordingto the invention. The co-catalyst is preferably a compound of group 13of the periodic table (IUPAC, version 2013), such as for example analuminum compound, e.g. an organo aluminum or aluminum halide compound.An example of a suitable organo aluminium compound is an aluminum alkylor aluminum alkyl halide compound. Accordingly, in one specificembodiment the co-catalyst (Co) is a trialkylaluminium, liketriethylaluminium (TEAL), dialkyl aluminium chloride or alkyl aluminiumdichloride or mixtures thereof. In one specific embodiment theco-catalyst (Co) is triethylaluminium (TEAL).

Generally, the molar ratio between the co-catalyst (Co) and the externaldonor (ED) [Co/ED] and/or the molar ratio between the co-catalyst (Co)and the transition metal (TM) [Co/TM] is carefully chosen for eachprocess. The molar ratio between the co-catalyst

(Co) and the external donor (ED), [Co/ED] can suitably be in the rangeof 2.5 to 50.0 mol/mol, preferably in the range of 4.0 to 35.0 mol/mol,more preferably in the range of 5.0 to 30.0 mol/mol. A suitable lowerlimit can be 2.5 mol/mol, preferably 4.0 mol/mol, more preferably 5.0mol/mol. A suitable upper limit can be 50.0 mol/mol, preferably 35.0mol/mol, more preferably 30.0 mol/mol. The lower and upper indicatedvalues of the ranges are included.

The molar ratio between the co-catalyst (Co) and the transition metal(TM), [Co/TM] can suitably be in the range of 20.0 to 500.0 mol/mol,preferably in the range of 50.0 to 400.0 mol/mol, more preferably in therange of 100.0 to 300.0 mol/mol. A suitable lower limit can be 20.0mol/mol, preferably 50.0 mol/mol, more preferably 100.0 mol/mol. Asuitable upper limit can be 500.0 mol/mol, preferably 400.0 mol/mol,more preferably 300.0 mol/mol. The lower and upper indicated values ofthe ranges are included.

Polypropylene Composition

According to the present invention, the material produced after thesecond reactor (i.e. the sum of the first and second polymer fractions)or the material produced after the third reactor (i.e. the sum of thefirst to third polymer fractions) may be recovered from thepolymerization process. It can be extruded in the presence of at leastone nucleating agent in order to produce the required polypropylenecomposition for cap or closure manufacture.

The extruder, where the extrusion step is carried out, may be anyextruder known in the art. The extruder may thus be a single screwextruder; a twin screw extruder, such as a co-rotating twin screwextruder or a counter-rotating twin screw extruder; or a multi-screwextruder, such as a ring extruder. Preferably the extruder is a singlescrew extruder or a twin screw extruder. Especially preferred extruderis a co-rotating twin screw extruder.

The extruder typically comprises a feed zone, a melting zone, a mixingzone and optionally a die zone.

The extruder typically has a length over diameter ratio, L/D, of up to60:1, preferably of up to 40:1.

The extruder may also have one or more feed ports for introducingfurther components, such as for example additives, into the extruder.The location of such additional feed ports depends on the type ofmaterial added through the port.

Examples of additives include, but are not limited to, stabilizers suchas antioxidants (for example sterically hindered phenols,phosphites/phosphonites, sulphur containing antioxidants, alkyl radicalscavengers, aromatic amines, hindered amine stabilizers, or blendsthereof), metal deactivators (for example Irganox® MD 1024), or UVstabilizers (for example hindered amine light stabilizers). Othertypical additives are modifiers such as antistatic or antifogging agents(for example ethoxylated amines and amides or glycerol esters), acidscavengers (for example Ca-stearate), blowing agents, cling agents (forexample polyisobutene), lubricants and resins (for example ionomerwaxes, polyethylene- and ethylene copolymer waxes, Fischer Tropschwaxes, montan-based waxes, fluoro-based compounds, or paraffin waxes),as well as slip and antiblocking agents (for example erucamide,oleamide, talc, natural silica and synthetic silica or zeolites) andmixtures thereof.

Generally, the total amount of additives introduced into the extruderduring the process according to the present invention, is not more than5.0 wt %, preferably not more than 2.0 wt %, more preferably not morethan 1.5 wt %. The amount of additives is relative to the total amountof polypropylene composition introduced into the extruder.

In the process according to the invention, the polymer available afterformation of the second propylene polymer fraction or third propylenepolymer fraction is extruded at a temperature which is higher than themelting temperature of the polymer but lower than the decompositiontemperature of the polymer. Suitably, the polymer composition isextruded at a temperature at least 30° C. higher than the meltingtemperature of the polymer composition, preferably the polymercomposition is extruded at a temperature at least 40° C. higher than themelting temperature of the polymer composition, more preferably thepolymer composition is extruded at a temperature at least 50° C. higherthan the melting temperature of the polymer composition, but lower thanthe decomposition temperature of the polymer composition, i.e. lowerthan 300° C. Most preferred temperatures are 200 to 250° C., such as 220to 240° C.

In the process according to the invention, the polymer composition isextruded in the presence of an amount of the at least one nucleatingagent, preferably in the range of from 0.01 to 1.0 wt %, preferably inthe range of from 0.03 to 0.9 wt %, more preferably in the range of from0.05 to 0.8 wt %. The amount of the at least one nucleating agent isrelative to the total amount of polypropylene composition according tothe invention.

The nucleating agent is generally selected from the group consisting of:

-   -   (i) salts of monocarboxylic acids and polycarboxylic acids, e.g.        sodium benzoate or aluminum tert-butylbenzoate,    -   (ii) dibenzylidenesorbitol (e.g. 1,3:2,4 dibenzylidenesorbitol)        and C₁-C₈-alkyl-substituted dibenzylidenesorbitol derivatives,        such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol        or dimethyldibenzylidenesorbitol (e.g. 1,3:2,4        di(methylbenzylidene) sorbitol), or substituted        nonitol-derivatives, such as        1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol,    -   (iii) salts of diesters of phosphoric acid, e.g. sodium        2,2′-methylenebis (4, 6,-di-tert-butylphenyl) phosphate or        aluminium-hydroxy-bis[2,2′-methylene-bis(4,6-di-t-butylphenyl)phosphate],    -   (iv) vinylcycloalkane polymer and vinylalkane polymer, and    -   (v) mixtures thereof.

Preferably, the nucleating agent is a dibenzylidenesorbitol (e.g.1,3:2,4 dibenzylidenesorbitol) or a C₁-C₈-alkyl-substituteddibenzylidenesorbitol derivative, such as methyldibenzylidenesorbitol,ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g.1,3:2,4 di(methylbenzylidene) sorbitol) or a substitutednonitol-derivative, such as1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl) methylene]-nonitol.

The at least one nucleating agent is generally fed into the extruder viathe feed zone. However, the at least one nucleating agent may be fedinto the extruder via the one or more feed ports comprised in theextruder, e.g., via a side feeder.

At the end of the extruder, a polypropylene composition melt isobtained. The inventive polypropylene composition melt might then bepassed through a die in the optional die zone of the extruder. When theinventive polypropylene composition melt is passed through the die it isgenerally further cooled down and pelletized.

The die zone typically comprises a die plate, which is generally a thickmetal disk having multiple holes. The holes are parallel to the screwaxis.

The pelletizer is generally a strand pelletizer or an underwaterpelletizer.

In any embodiment, the polypropylene composition obtainable, preferablyobtained, by the process according to the invention generally has onecomonomer only, ethylene.

In any embodiment, the polypropylene composition obtainable, preferablyobtained by the process according to the invention generally has acomonomer content in the range of from 2.2 to 5.0 wt %, preferably inthe range of from 2.5 to 4.8 wt %, more preferably in the range of from2.8 to 4.5 wt %. Most preferred amounts are 3.2 to 4.2 or 3.4 to 4.0 wt%. The comonomer content is relative to the total amount of monomerspresent in the polypropylene composition.

In any embodiment, the polypropylene composition obtainable, preferablyobtained, by the process according to the invention has a melt flow rate(MFR₂) in the range of from 12 to 60 g/10 min, preferably in the rangeof from 15 to 35 g/10 min, more preferably in the range of from 15 to 30g/10 min. The MFR₂ is determined according to ISO 1133, at a temperatureof 230° C. and under a load of 2.16 kg.

In any embodiment, the polypropylene composition preferably has acrystallisation temperature (Tc) of at least 90° C. when subjected to acooling rate of 10 K/s.

In any embodiment, the polypropylene composition preferably has acrystallisation temperature (Tc) of at least 55° C. when subjected to acooling rate of 100 K/s. In any embodiment, the polypropylenecomposition preferably has a crystallisation temperature (Tc) of atleast 40° C. when subjected to a cooling rate of 300 K/s.

The polypropylene composition preferably has a crystallisationtemperature (Tc) of at least 95° C. when subjected to a cooling rate of10 K/s.

In any embodiment, the polypropylene composition preferably has acrystallisation temperature (Tc) of at least 75° C. when subjected to acooling rate of 100 K/s.

In any embodiment, the polypropylene composition preferably has acrystallisation temperature (Tc) of at least 55° C. when subjected to acooling rate of 300 K/s.

In any embodiment, the polypropylene composition preferably has acrystallisation temperature (Tc) of at least 90° C. when subjected to acooling rate of 10 K/s.,

a crystallisation temperature (Tc) of at least 55° C. when subjected toa cooling rate of 100 K/s.; and

a crystallisation temperature (Tc) of at least 40° C. when subjected toa cooling rate of 300 K/s.

In any embodiment, the polypropylene composition preferably has

a crystallisation temperature (Tc) of 90 to 140° C. when subjected to acooling rate of 10 K/s.,

a crystallisation temperature (Tc) of 55 to 100° C. when subjected to acooling rate of 100 K/s.; and

a crystallisation temperature (Tc) of 40 to 80° C. when subjected to acooling rate of 300 K/s.

In any embodiment, the polypropylene composition preferably has

a crystallisation temperature (Tc) of at least 95° C. when subjected toa cooling rate of 10 K/s.,

a crystallisation temperature (Tc) of at least 75° C. when subjected toa cooling rate of 100 K/s.; and

a crystallisation temperature (Tc) of at least 55° C. when subjected toa cooling rate of 300 K/s.

In any embodiment, the polypropylene composition preferably has acrystallisation temperature (Tc) of at least 50° C. when subjected to acooling rate in the range of 100 to 600 K/s.

In any embodiment and at any cooling rate, the polypropylene compositionpreferably has a crystallisation temperature (Tc) of less than 140° C.

Caps and Closures

The present invention requires the formation of a cap or closure fromthe polypropylene composition. Cap or closure preparation can occur viaknown methods, e.g. injection or compression moulding of the extrudedpolypropylene composition. A preferred article is a closure cap, a screwcap or a closure system for food or fluid packaging. Preferably the capor closure is injection moulded.

A particular feature of the invention is that the polypropylenecomposition has high crystallisation temperature (Tc) across a range ofcooling rates. It is especially preferred if the cooling rate during thecap or closure manufacturing process is between 50 to 600 K/s, such as100 to 600 K/s, especially 100 to 300 K/s.

Such rapid cooling rates lead to quick cycle times. Whilst cycle timeswill depend on the cap or closure in question cycle times of less than6.0 secs, e.g. 4.5 to 6.0 secs, especially 4.7 to 6.0 secs areenvisaged. The term cycle time refers to the time between injection ofthe polypropylene composition into the mould, cooling the composition,ejecting the cap or closure that forms to the start of the injection ofcomposition for the next article.

The invention will now be described with reference to the following nonlimiting examples and figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the relationship between crystallsiaiton temperature andcooling rate for the inventive and comparative examples.

FIG. 2(a) is a Schematic diagram of the CRYSTEX QC instrument and FIG.2(b) shows elution of the EP copolymer sample and obtained soluble andcrystalline fractions in the TREF column (column filled with inertmaterial e.g. glass beads) (see Del Hierro, P.; Ortin, A.; Monrabal, B.;‘Soluble Fraction Analysis in polypropylene, The Column AdvanstarPublications, February 2014. Pages 18-23).

EXAMPLES I. Measuring Methods

a) Melt Flow Rate

The melt flow rate (MFR) is determined according to ISO 1133 and isindicated in g/10 min. The MFR is an indication of the flowability andhence the processability of the polymer. The higher the melt flow rate,the lower the viscosity of the polymer. The MFR₂ of polypropylene isdetermined ata temperature of 230° C. and under a load of 2.16 kg.

b) DSC Analysis

The crystallisation temperature is measured with a TA Instrument Q2000differential scanning calorimetry device (DSC) according to ISO 11357/3on 5 to 10 mg samples, under 50 mL/min of nitrogen atmosphere.Crystallisation temperatures were obtained in a heat/cool/heat cyclewith a scan rate of 10° C./min between 30° C. and 225° C.Crystallisation temperatures were taken as the peaks of the endothermsand exotherms in the cooling step and the second heating steprespectively.

Fast Scanning Calorimetry (FSC)

A power-compensation-type differential scanning calorimeter Flash DSC1from MettlerToledo was used to analyze isothermally and non-isothermallythe crystallization behavior in the range of cooling rates from 10° to10³ K s−1. The instrument was attached to a Huber intracooler TC45, toallow cooling down to about −100° C. The preparation of samples includescutting of thin sections with thickness of 10 to 15 pm from the surfaceof pellets. The specimens were heated to 200° C., kept at thistemperature for 0.1 s and cooled at different cooling rates to −33° C.which is below the glass transition temperature of the mobile amorphousfraction of iPP. The furnace of the instrument was purged with drynitrogen gas at a flow rate of 30 mL /min. The sensors were subjected tothe so called conditioning procedure which includes several heating andcooling runs. Afterwards, a temperature correction of the sensor wasperformed. Before loading the sample a thin layer of silicon oil wasspread on the heating area of the sample sensor to improve the thermalcontact between the sensor and the sample. The sensors are developed byXensor Integration (Netherlands). Each sensor is supported by a ceramicbase plate for easy handling. The total area of the chip is 5.0×3.3 mm²;it contains two separate silicon nitride/oxide membranes with an area of1.7×1.7 mm² and a thickness of 2.1 mm each, being surrounded by asilicon frame of 300 μm thickness, serving as a heat sink. In thepresent work additional calibrations were not performed. Further detailsto the technique as such are given here:

-   E. lervolino, A. van Herwaarden, F. van Herwaarden, E. van de    Kerkhof, P. van Grinsven, A. Leenaers, V. Mathot, P. Sarro.    Temperature calibration and electrical characterization of the    differential scanning calorimeter chip UFS1 for the Mettler-Toledo    Flash DSC 1. Thermochim. Acta 522, 53-59 (2011). V. Mathot, M.    Pyda, T. Pijpers, G. Poel, E. van de Kerkhof, S. van Herwaarden, F.    van Herwaarden, A. Leenaers. The Flash DSC 1, a power compensation    twin-type, chip-based fast scanning calorimeter (FSC): First    findings of polymers. Thermochim. Acta 552, 36-45 (2011).-   M. van Drongelen, T. Meijer-Vissers, D. Cavallo, G. Portale, G.    Vanden Poel, R. Androsch R. Microfocus wide-angle X-ray scattering    of polymers crystallized in a fast scanning chip calorimeter.    Thermochim Acta 563, 33-37 (2013).

c) Comonomer Content

Poly(propylene-co-ethylene)—Ethylene Content by IR Spectroscopy

Quantitative infrared (IR) spectroscopy was used to quantify theethylene content of the poly(ethylene-co-propene) copolymers throughcalibration to a primary method.

Calibration was facilitated through the use of a set of in-housenon-commercial calibration standards of known ethylene contentsdetermined by quantitative ¹³C solution-state nuclear magnetic resonance(NMR) spectroscopy. The calibration procedure was undertaken in theconventional manner well documented in the literature. The calibrationset consisted of 38 calibration standards with ethylene contents ranging0.2-75.0 wt % produced at either pilot or full scale under a variety ofconditions. The calibration set was selected to reflect the typicalvariety of copolymers encountered by the final quantitative IRspectroscopy method.

Quantitative IR spectra were recorded in the solid-state using a BrukerVertex 70 FTIR spectrometer. Spectra were recorded on 25×25 mm squarefilms of 300 um thickness prepared by compression moulding at 180-210°C. and 4-6 mPa. For samples with very high ethylene contents (>50 mol %)100 um thick films were used. Standard transmission FTIR spectroscopywas employed using a spectral range of 5000-500 cm⁻¹, an aperture of 6mm, a spectral resolution of 2 cm⁻¹, 16 background scans, 16 spectrumscans, an interferogram zero filling factor of 64 and Blackmann-Harris3-term apodisation.

Quantitative analysis was undertaken using the total area of the CH₂rocking deformations at 730 and 720 cm⁻¹ (A_(Q)) corresponding to(CH₂)>₂ structural units (integration method G, limits 762 and 694cm⁻¹). The quantitative band was normalised to the area of the CH bandat 4323 cm⁻¹ (AR) corresponding to CH structural units (integrationmethod G, limits 4650, 4007 cm⁻¹). The ethylene content in units ofweight percent was then predicted from the normalised absorption(A_(Q)/A_(R)) using a quadratic calibration curve. The calibration curvehaving previously been constructed by ordinary least squares (OLS)regression of the normalised absorptions and primary comonomer contentsmeasured on the calibration set.

Poly(propylene-co-ethylene)—Ethylene Content for Calibration Using ¹³CNMR Spectroscopy

Quantitative ¹³C{¹H} NMR spectra were recorded in the solution-stateusing a Bruker Avance III 400 NMR spectrometer operating at 400.15 and100.62 MHz for ¹H and ¹³C respectively. All spectra were recorded usinga ¹³C optimised 10 mm extended temperature probehead at 125° C. usingnitrogen gas for all pneumatics. Approximately 200 mg of material wasdissolved in 3 ml of 1,2-tetrachloroethane-d₂ (TCE-d₂) along withchromium (III) acetylacetonate (Cr(acac)₃) resulting in a 65 mM solutionof relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V.,Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution,after initial sample preparation in a heat block, the NMR tube wasfurther heated in a rotatory oven for at least 1 hour. Upon insertioninto the magnet the tube was spun at 10 Hz. This setup was chosenprimarily for the high resolution and quantitatively needed for accurateethylene content quantification. Standard single-pulse excitation wasemployed without NOE, using an optimised tip angle, 1 s recycle delayand a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu,X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag.Reson. 187 (2007) 225, Busico, V., Carbonniere, P., Cipullo, R.,Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007,28, 1128). A total of 6144 (6 k) transients were acquired per spectra.Quantitative ¹³C{¹H} NMR spectra were processed, integrated and relevantquantitative properties determined from the integrals. All chemicalshifts were indirectly referenced to the central methylene group of theethylene block (EEE) at 30.00 ppm using the chemical shift of thesolvent. This approach allowed comparable referencing even when thisstructural unit was not present. Characteristic signals corresponding tothe incorporation of ethylene were observed (Cheng, H. N.,Macromolecules 17 (1984), 1950) and the comonomer fraction calculated asthe fraction of ethylene in the polymer with respect to all monomer inthe polymer: fE=(E/(P+E) The comonomer fraction was quantified using themethod of Wang et. al. (VVang, W-J., Zhu, S., Macromolecules 33 (2000),1157) through integration of multiple signals across the whole spectralregion in the ¹³C{¹H} spectra. This method was chosen for its robustnature and ability to account for the presence of regio-defects whenneeded. Integral regions were slightly adjusted to increaseapplicability across the whole range of encountered comonomer contents.The mole percent comonomer incorporation was calculated from the molefraction: E [mol %]=100*fE. The weight percent comonomer incorporationwas calculated from the mole fraction: E [wt%]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

d) Xylene Soluble Content (XCS, Wt %)

The content of the polymer soluble in xylene is determined according toISO 16152; 5^(th) edition; 2005-07-01 at 25° C.

e) Tensile Modulus

Tensile Modulus is measured according to ISO 527-1:2012/IS0527-2:2012 at23° C. and at a cross head speed=50 mm/min; using injection moulded testspecimens as described in EN ISO 1873-2 (dog bone shape, 4 mmthickness).

f) Charpy Notched Impact

Charpy notched impact strength is determined according to ISO 179/1eA at23° C. on injection moulded test specimens as described in EN ISO 1873-2(80×10×4 mm).

g) Haze

Haze is determined according to ASTM D1003 on injection moulded plaqueshaving 1 mm thickness and 60×60 mm² area produced as described in EN ISO1873-2.

h) Crystex Analysis

Crystalline and Soluble Fractions Method

The crystalline (CF) and soluble fractions (SF) of the polypropylene(PP) compositions as well as the comonomer content and intrinsicviscosities of the respective fractions were analysed by the CRYSTEX QC,Polymer Char (Valencia, Spain).

A schematic representation of the CRYSTEX QC instrument is shown in FIG.2a . The crystalline and amorphous fractions are separated throughtemperature cycles of dissolution at 160° C., crystallization at 40° C.and re-dissolution in a 1,2,4-trichlorobenzene (1,2,4-TCB) at 160° C. asshown in FIG. 1 b. Quantification of SF and CF and determination ofethylene content (C2) are achieved by means of an infrared detector(IR4) and an online 2-capillary viscometer which is used for thedetermination of the intrinsic viscosity (IV).

The IR4 detector is a multiple wavelength detector detecting IRabsorbance at two different bands (CH3 and CH2) for the determination ofthe concentration and the Ethylene content in Ethylene-Propylenecopolymers. 1R4 detector is calibrated with series of 8 EP copolymerswith known Ethylene content in the range of 2 wt.-% to 69 wt.-%(determined by 13C-NMR) and various concentration between 2 and 13 mg/mlfor each used EP copolymer used for calibration.

The amount of Soluble fraction (SF) and Crystalline Fraction (CF) arecorrelated through the XS calibration to the “Xylene Cold Soluble” (XCS)quantity and respectively Xylene Cold Insoluble (XCI) fractions,determined according to standard gravimetric method as per ISO16152. XScalibration is achieved by testing various EP copolymers with XS contentin the range 2-31 Wt %.

The intrinsic viscosity (IV) of the parent EP copolymer and its solubleand crystalline fractions are determined with a use of an online2-capillary viscometer and are correlated to corresponding IV'sdetermined by standard method in decalin according to ISO 1628.Calibration is achieved with various EP PP copolymers with IV=2-4 dL/g.

A sample of the PP composition to be analysed is weighed out inconcentrations of 10 mg/ml to 20 mg/ml. After automated filling of thevial with 1,2,4-TCB containing 250 mg/l 2,6-tert-butyl-4-methylphenol(BHT) as antioxidant, the sample is dissolved at 160° C. until completedissolution is achieved, usually for 60 min, with constant stirring of800 rpm.

As shown in a FIGS. 2a and 2b , a defined volume of the sample solutionis injected into the column filled with inert support where thecrystallization of the sample and separation of the soluble fractionfrom the crystalline part is taking place. This process is repeated twotimes. During the first injection the whole sample is measured at hightemperature, determining the IV[dl/g] and the C2[wt %] of the PPcomposition. During the second injection the soluble fraction (at lowtemperature) and the crystalline fraction (at high temperature) with thecrystallization cycle are measured (Wt % SF, Wt % C2, IV).

EP means ethylene propylene copolymer.PP means polypropylene.

II. Inventive Example

a) Catalyst ppreparation

For the preparation of the catalyst 3.4 litre of 2-ethylhexanol and 810ml of propylene glycol butyl monoether (in a molar ratio 4/1) were addedto a 20.0 l reactor. Then 7.8 litre of a 20.0% solution in toluene ofBEM (butyl ethyl magnesium) provided by Crompton GmbH, were slowly addedto the well stirred alcohol mixture. During the addition, thetemperature was kept at 10.0° C. After addition, the temperature of thereaction mixture was raised to 60.0° C. and mixing was continued at thistemperature for 30 minutes. Finally after cooling to room temperaturethe obtained Mg-alkoxide was transferred to a storage vessel.

21.2 g of Mg alkoxide prepared above was mixed with 4.0 mlbis(2-ethylhexyl) citraconate for 5 min. After mixing the obtained Mgcomplex was used immediately in the preparation of the catalystcomponent.

19.5 ml of titanium tetrachloride was placed in a 300 ml reactorequipped with a mechanical stirrer at 25.0° C. Mixing speed was adjustedto 170 rpm. 26.0 g of Mg-complex prepared above was added within 30minutes keeping the temperature at 25.0° C. 3.0 ml of Viscoplex® 1-254and 1.0 ml of a toluene solution with 2 mg Necadd 447™ was added. Then24.0 ml of heptane was added to form an emulsion. Mixing was continuedfor 30 minutes at 25.0° C., after which the reactor temperature wasraised to 90.0° C. within 30 minutes. The reaction mixture was stirredfor a further 30 minutes at 90.0° C. Afterwards stirring was stopped andthe reaction mixture was allowed to settle for 15 minutes at 90.0° C.The solid material was washed 5 times: washings were made at 80.0° C.under stirring for 30 min with 170 rpm. After stirring was stopped thereaction mixture was allowed to settle for 20-30 minutes and followed bysiphoning.

Wash 1: washing was made with a mixture of 100 ml of toluene and 1 mldonor

Wash 2: washing was made with a mixture of 30 ml of TiCl4 and 1 ml ofdonor.

Wash 3: washing was made with 100 ml of toluene.

Wash 4: washing was made with 60 ml of heptane.

Wash 5: washing was made with 60 ml of heptane under 10 minutesstirring.

Afterwards stirring was stopped and the reaction mixture was allowed tosettle for 10 minutes while decreasing the temperature to 70° C. withsubsequent siphoning, followed by N₂ sparging for 20 minutes to yield anair sensitive powder.

Inventive example (IE) was produced in a pilot plant with aprepolymerization reactor, one slurry loop reactor and two gas phasereactors. The solid catalyst component described above along withtriethyl-aluminium (TEAL) as co-catalyst and dicyclopentyl dimethoxysilane (D-donor) as external donor, were used in the inventive process.

The polymerization process conditions and properties of the propylenepolymer fractions are described in Table 1.

The polypropylene composition is then extruded with a nucleating agentin a co-rotating twin screw extruder type Coperion ZSK 40 (screwdiameter 40 mm, L/D ratio 38). The temperatures in the extruder were inthe range of 190-230° C. In the inventive example, 0.05 wt % of Irganox1010 (Pentaerythrityl-tetrakis(3-(3′,5′-di-tert.butyl-4-hydroxyphenyl)-propionate, CAS No. 6683-19-8, commerciallyavailable from BASF AG, Germany), 0.05 wt % of Irgafos 168 (Tris(2,4-di-t-butylphenyl) phosphite, CAS No. 31570-04-4, commerciallyavailable from BASF AG, Germany), 0.10 wt % of Calcium stearate (CAS.No. 1592-23-0, commercially available under the trade name Ceasit FIfrom Baerlocher GmbH, Germany) and 0.06 wt % of Glycerol monostearate(CAS No. 97593-29-8, commercially available with 90% purity under thetrade name Grindsted PS 426 from Danisco A/S, Denmark), 0.17 wt % Millad3988 (CAS No. 135861-56-2, Milliken) were added to the extruder asadditives. 0.3 ppm of Poly Vinyl Cyclo Hexane (PVCH) was added via anucleating masterbatch

Said nucleating masterbatch is a PP-homopolymer, MFR 20, and comprisesca 15 ppm of PVCH as polymeric nucleating agent.

Following the extrusion step and after solidification of the strands ina water bath, the resulting polypropylene composition was pelletized ina strand pelletizer.

TABLE 1 Polymerization process conditions and properties of thepropylene polymer fractions IE1 Pre-polymerization reactor Temperature[° C.] 30 Catalyst feed [g/h] 4.4 TEAL/propylene [g/t propylene] 170Residence Time [min] 20 Loop reactor (first propylene polymer fraction)Temperature [° C.] 70 Pressure [kPa] 5400 Split [%] 46.8 H₂/C₃ ratio[mol/kmol] 1.9 C₂/C₃ ratio [mol/kmol] 3.2 MFR₂ [g/10 min] 22 C₂ contentafter loop [wt %] 0.5 reactor First gas-phase reactor - Temperature [°C.] 80 Pressure [kPa] 1820 Split [%] 43.2 H₂/C₃ ratio [mol/kmol] 27.1C₂/C₃ ratio [mol/kmol] 7.9 MFR₂ [g/10 min] 17.4 C₂ content after 1^(st)gas [wt %] 1.4 hase reactor Second gas-phase reactor - Temperature [°C.] 80 Pressure [kPa] 2500 Split [%] 10 H₂/C₃ ratio [mol/kmol] 27.5C₂/C₃ ratio [mol/kmol] 68.9 MFR₂ [g/10 min] 17.3 C₂ content final [wt %]2.5 C2 ratio (final/fraction 1) 0.2 *Split relates to the amount ofpropylene polymer produced in each specific reactor.

Its properties are compared to RE420MO (a polypropylene random copolymerof MFR 13 g/10 min and IE2 of WO2009/021686).

Results are presented in FIG. 1 and table 2. As can be seen in FIG. 1,the inventive example shows mono-crystalline behaviour (no transition tomesophase) with cooling rate up to 600 k/s.

The comparative example has a much lower cooling rate. Starting from 50K/s, a new crystallisation peak appears at a much lower Tc which is thecrystallisation of the mesophase. Crystallisation stops at the coolingrate of 200 k/s.

IE1 has much faster crystallisation rate measured as Tc with a broadercooling rate range.

TABLE 2 Polypropylene composition properties. CE IE1 MFR-final g/10 min13 17.3 Tensile modulus MPa 1124 1398 Tensile strength MPa 29 33 NIS-BkJ/m2 6.2 5.8 Haze-1 mm % 16 18.1 SF wt % 8.02 8.2 C2 wt % 3.03 2.5C2(SF) wt % 15.3 12.4 C2(CF) wt % 2.5 1.7 IV dl/g 1.7 1.6 IV(SF) dl/g0.5 0.6 IV(CF) dl/g 1.8 1.7 Top load force on cap N 1553 1741

Screw caps type PCO 1810 were made by injection moulding thepolypropylene composition on an ENGEL Speed 180/45 injection mouldingmachine, equipped with a 12 cavity tool for screw caps.

The tool was supplied by Husky/KTW.

Injection moulding was done with an injection speed: 170 cm³/sec, aholding pressure. 860 bar and melt temperature of 230° C. or 240° C. andtool temperature of 12° C.

Cycle and cooling times are given in Table 3 to 5.

TABLE 3 Crystallisation temperatures at fast cooling rates Cooling rate[K/sec] CE (RE420MO) IE K/s Tc. mono Tc. meso Tc. mono 0.05 124 0.16 120127 0.5 116 1 102 116 2 97 113 3 94 112 4 91 110 5 90 108 6 89 108 7 88106 8 86 106 9 85 105 10 84 104 20 81 99 30 75 96 40 72 93 50 70 26 9160 65 23 89 70 59 21 87 80 58 19 85 90 55 17 84 100 54 15 83 200 52 1172 300 63 400 58 500 57 600 53

TABLE 4 Processing behaviour of the Inventive Example at various cycletimes and mass temperatures Inventive example Cooling Cycle-time timeMass Temperature Mass Temperature [sec] [sec.] 240° C. 230° C. 5.1 2.5Good (minimal Angel Good (minimal Angel Hair & high tips) Hair & hightips) 4.9 2.3 Good (High Tips) Good (minimal Angel Hair & high tips) 4.72.1 sometimes demoulding sometimes demoulding problems problems 4.5 1.9Demoulding problems Demoulding problems (ring tears off) 4.3 1.7 NotPossible Demoulding problems (ring tears off)

TABLE 5 Processing behaviour of the comparative Example at various cycletimes and mass temperatures Comparative Example Cooling Cycle-time timeMass Temperature Mass Temperature [sec] [sec.] 240° C. 230° C. 5.1 2.5Good (minimal Angel Good (minimal Angel Hair & high tips) Hair & hightips) 4.9 2.3 Demoulding Good (minimal Angel problems Hair & high tips)4.7 2.1 major demoulding Demoulding problems (ring problems tears off)4.5 1.9 Not Possible major demoulding problems (ring tears off) 4.3 1.7Not Possible Not Possible

1. A process for producing a cap or closure comprising obtaining apolypropylene composition by sequential polymerization comprising thesteps: A) polymerizing in a first reactor, preferably a slurry reactor,in the presence of a Ziegler-Natta catalyst, monomers comprisingpropylene and optionally one or more comonomers selected from ethyleneand C4-C10 alpha-olefins, to obtain a first propylene polymer fractionhaving a comonomer content in the range of 0.0 to 1.8 wt %, and a MFR2in the range of from 12.0 to 40.0 g/10 min, as measured according to ISO1133 at 230° C. under a load of 2.16 kg; B) polymerizing in a secondreactor, preferably a first gas-phase reactor, monomers comprisingpropylene and one or more comonomers selected from ethylene and C4-C10alpha-olefins, in the presence of the first propylene polymer fraction,to obtain a second propylene polymer fraction, wherein the polypropylenecomposition comprising said first and second propylene polymer fractionshas an MFR2 in the range of from 12.0 to 60.0 g/10 min, as measuredaccording to ISO 1133 at 230° C. under a load of 2.16 kg, has acomonomer content in the range of from 2.2 to 5.0 wt % and wherein theratio of the comonomer content of component A) to the comonomer contentof the polypropylene composition is 0.35 or less, C) melting, extrudingand moulding the polypropylene composition in the presence of at leastone nucleating agent to prepare a cap or closure; and D) exposing thecap or closure obtained in step (C) to a cooling rate of 50 K/s or more.2. A process for producing a cap or closure comprising obtaining apolypropylene composition by sequential polymerization comprising: A)polymerizing in a first reactor, preferably a slurry reactor, in thepresence of a Ziegler-Natta catalyst, monomers comprising propylene andoptionally one or more comonomers selected from ethylene and C4-C10alpha olefins, to obtain a first propylene polymer fraction having acomonomer content in the range of 0.0 to 1.8 wt %, and a MFR2 in therange of from 12.0 to 40.0 g/10 min, as measured according to ISO 1133at 230° C. under a load of 2.16 kg; (B) polymerizing in a secondreactor, preferably a first gas-phase reactor, monomers comprisingpropylene and one or more comonomers selected from ethylene andoptionally C4-C10 alpha olefins, in the presence of the first propylenepolymer fraction, to obtain a second propylene polymer fraction, (C)polymerizing in a third reactor, preferably a second gas-phase reactor,monomers comprising propylene and one or more comonomers selected fromethylene and optionally C4-C10 alpha olefins, in the presence of thesecond propylene polymer fraction to obtain a third propylene polymerfraction; wherein the polypropylene composition comprising said first,second and third propylene polymer fractions has an MFR2 in the range offrom 12.0 to 60.0 g/10 min, as measured according to ISO 1133 at 230° C.under a load of 2.16 kg, has a comonomer content in the range of from2.2 to 5.0 wt % and wherein the ratio of the comonomer content ofcomponent A) to the comonomer content of the polypropylene compositionis 0.35 or less, D) melting, extruding and moulding the polypropylenecomposition in the presence of at least one nucleating agent to preparea cap or closure; and E) exposing the cap or closure obtained in step(D) to a cooling rate of 50 K/s or more.
 3. The process according toclaim 1 or 2, wherein the polymerization is carried out in the presenceof a Ziegler-Natta catalyst which is free of a phthalic compound.
 4. Theprocess according to any one of the preceding claims, wherein thecomonomers are selected from solely ethylene.
 5. The process accordingto any one of the preceding claims, wherein the comonomer content of thepolypropylene composition is in the range of 2.2 to 4.5 wt %.
 6. Theprocess according to any one of the preceding claims, wherein thenucleating agent is present in the range of from 0.01 to 1.0 wt %,relative to the total amount of polypropylene composition.
 7. Theprocess according to any one of the preceding claims, wherein saidpolypropylene composition has a crystallisation temperature (Tc) of atleast 55° C. when subjected to a cooling rate of 100 K/s.; and acrystallisation temperature (Tc) of at least 40° C. when subjected to acooling rate of 300 K/s.
 8. A process as claimed in any preceding claimwherein the cooling rate is 100 to 600 K/s, preferably 100 to 300 K/s.9. A process as claimed in any preceding claim wherein the melting stepis effected at a temperature of at least 200° C.
 10. A process asclaimed in any preceding claim wherein the moulding in step C) or D) iseffected in a mould and after cooling step D) or E), the cap or closureis ejected from the mould and a new cap or closure is then formed in themould and subjected to cooling step D) or E).
 11. A process as claimedin claim 10 wherein the cycle time for each cap to be moulded, cooled,and ejected from the mould is 6.0 secs or less, e.g. 4.7 to 6.0 secs.12. A cap or closure comprising polypropylene composition and at leastone nucleating agent said polypropylene composition having a first homoor copolymer fraction, a second copolymer fraction and optionally athird copolymer fraction, said polypropylene composition having anethylene content of 2.2 to 5.0 wt % and wherein said polypropylenecomposition has a crystallisation temperature (Tc) of at least 90° C.when subjected to a cooling rate of 10 K/s. a crystallisationtemperature (Tc) of at least 55° C. when subjected to a cooling rate of100 K/s.; and a crystallisation temperature (Tc) of at least 40° C. whensubjected to a cooling rate of 300 K/s.
 13. A cap or closure as claimedin claim 12 wherein the polypropylene composition has an MFR2 in therange of from 12.0 to 60.0 g/10 min, as measured according to ISO 1133at 230° C. under a load of 2.16 kg, and wherein the ratio of thecomonomer content of the first homo or copolymer fraction to thecomonomer content of the polypropylene composition is 0.35 or less. 14.A cap or closure as claimed in claim 12 or 13 wherein said polypropylenecomposition comprises a first homo or copolymer fraction, a secondcopolymer fraction and a third copolymer fraction.
 15. A process forproducing a cap or closure comprising obtaining a polypropylenecomposition comprising a nucleating agent and a polypropylenecomposition having a first homo or copolymer fraction, a secondcopolymer fraction and optionally a third copolymer fraction, saidpolypropylene composition having an ethylene content of 2.2 to 5.0 wt %and, wherein said polypropylene composition has a crystallisationtemperature (Tc) of at least 90° C. when subjected to a cooling rate of10 K/s. a crystallisation temperature (Tc) of at least 55° C. whensubjected to a cooling rate of 100 K/s.; and a crystallisationtemperature (Tc) of at least 40° C. when subjected to a cooling rate of300 K/s; melting, extruding and moulding the polypropylene compositionin the presence of the at least one nucleating agent to prepare a cap orclosure; and exposing the cap or closure obtained to a cooling rate of100 K/s or more.
 16. A cap or closure obtained by a process according toclaims 1 to 11, such as a screw cap.
 17. Use of a polypropylenecomposition and at least one nucleating agent said polypropylenecomposition having a first homo or copolymer fraction, a secondcopolymer fraction and optionally a third copolymer fraction, saidpolypropylene composition having an ethylene content of 2.2 to 5.0 wt %and, wherein said polypropylene composition has a crystallisationtemperature (Tc) of at least 90° C. when subjected to a cooling rate of10 K/s. a crystallisation temperature (Tc) of at least 55° C. whensubjected to a cooling rate of 100 K/s.; and a crystallisationtemperature (Tc) of at least 40° C. when subjected to a cooling rate of300 K/s; to reduce the cycle time in cap or closure production.